Abstract

We investigated interference and exploitative competition between endangered San Joaquin kit foxes (Vulpes macrotis mutica) and nonnative red foxes (V. vulpes). Seven kit foxes and 16 red foxes were radio-collared and tracked via radiotelemetry near Lost Hills, California. One kit fox was killed by a red fox. Home ranges of the 2 species did not overlap extensively. Although both species used similar habitats, they used different parcels of land. Kit foxes and red foxes primarily consumed rodents on the study site, and dietary overlap was considerable. Red foxes also may have been using dens formerly used by kit foxes. Thus, red foxes were engaging in both interference and exploitative competition with kit foxes, and red foxes constitute a potentially significant threat to kit foxes. Coyotes (Canis latrans) co-occur with kit foxes and may limit red fox abundance and distribution. Therefore, although they occasionally kill kit foxes, the presence of coyotes may benefit kit foxes by excluding red foxes.